What is a circular bond beam? What is that made of and how does it integrate into the bags?
Bond beams can be created in a variety of ways, but probably to best with a circular structure would be to form a trough at least 6″ deep and as wide as the bags on top of them, suspend two rings of 1/2″ rebar running down the middle of it, and then pour this full of concrete. Periodic rebar pins pounded down into the bags, with their tops bent over in such a way that they will also become imbedded in the concrete, will connect this bond beam with the circular wall.
